1. Field of the Invention
The present invention relates to a propeller for use in a boat and more specifically, to a propeller that has shock-absorbing effect and can bear relatively higher torsion.
2. Description of the Related Art
FIG. 7 shows a conventional propeller 80 for use in a boat according to a prior art. The propeller 80 comprises a propeller shaft 81 inside which a shaft sleeve 82 is firmly installed. An adapter 83 is disposed inside the shaft sleeve 82. A driving shaft 84 of the boat passes through the adapter 83 and is fastened to the adapter 83 by a tab washer 85 and a lock nut 86. Accordingly, the adapter 83 and the shaft sleeve 82 can be driven to rotate by an engine of the boat through the driving shaft 84, resulting in a synchronous rotation of the propeller shaft 81.
According to this design, the shaft sleeve 82 is made of rigid materials. If the propeller 80 bumps hard things during rotation, the shaft sleeve 82 may be broken, or even that the driving shaft 84 of the engine may be damaged. Besides, if the driving shaft 84 outputs an exceeding torsion or receives an extreme impact suddenly, the shaft sleeve 82 may be also broken because the shaft sleeve 82 is driven by the adapter 83, which is driven by the driving shaft 84. If the shaft sleeve 82 is broken, the adapter 83 cannot run well. Thus, the conventional design of the propeller 80 is unable to be connected to a high-powered engine due to this potential defect. In addition, the adapter 83 and the shaft sleeve 82 must be coaxially aligned with the driving shaft 84 when they are assembled. However, because the adapter 83 and the shaft sleeve 82 are independently produced, any size inaccuracy in production of the adapter 83 or the shaft sleeve 82 will cause a possible clearance of assembly among the shaft sleeve 82, the adapter 83 and the driving shaft 84, resulting in a working vibration when the shaft sleeve 82 and the adapter 83 are driven to rotate by the driving shaft 84 in high speed.